Next-generation sequencing

Next-generation sequencing (NGS) is the collective name used for a diverse group of technologies that were developed after Sanger sequencing. Although it is widely used, the term NGS is not particularly accurate or descriptive; it also leads to the problem of what we should call the next type of sequencing technology when it comes along: next-next-generation sequencing?

The term NGS encompasses several different short-read massively parallel sequencing technologies, as well as several long-read sequencing technologies. Using these individual terms, rather than NGS, is more technically accurate.

Short-read sequencing breaks the genome into small fragments of about 50 to 300 bases in length for sequencing.

Massively parallel sequencing is a term used to describe modern high-throughput sequencing techniques that read the sequence of millions of short fragments of DNA or RNA at the same time.

Long-read sequencing can sequence long strands of more than 10,000 bases of DNA or RNA in one go, without breaking it up into smaller fragments.

NGS technologies are used clinically for whole genome sequencing (WGS), whole exome sequencing (WES), gene panel testing and increasingly for single gene testing.

These genomic technologies have transformed the fields of oncology, rare disease, infectious disease and prenatal diagnostics, and are increasingly becoming an integral part of mainstream clinical practice across all healthcare specialties.

NGS is also extensively used for research, enabling an era of gene discovery and diagnosis of rare monogenic conditions, and the identification and diagnosis of genetic factors contributing to common complex disease.

The form of NGS predominantly used by NHS clinical diagnostic labs at present is called short-read sequencing. Increasingly, however, long-read sequencing technology is being explored for clinical applications because it has several technical advantages over short-read sequencing.

• NGS is the collective name of a diverse range of sequencing technologies that were developed after Sanger sequencing.
• It is more accurate to use other terms to describe these technologies – for example, massively parallel sequencing and long-read sequencing.

For clinicians

• Association for Clinical Genetic Science: Practice guidelines for targeted next-generation sequencing analysis and interpretation (PDF, 13 pages)
• Applied Biological Materials: Next generation sequencing (NGS) – An introduction (video, 2 minutes 47 seconds)
• European Society of Human Genetics: A guide to genetic tests that are used to examine many genes at the same time (PDF, seven pages)

References:

• Muzzey D, Evans EA and Lieber C. ‘Understanding the basics of NGS: From mechanism to variant calling‘. Current Genetic Medicine Reports 2015: volume 3, issue 4, pages 158–165. DOI: 10.1007/s40142-015-0076-8
• Shendure J, Findlay GM and Snyder MW. ‘Genomic medicine – progress, pitfalls and promise‘. Cell 2019: volume 177, issue 1, pages 45–57. DOI: 10.1016/j.cell.2019.02.003